XML 121 R64.htm IDEA: XBRL DOCUMENT v2.4.1.9
Investments Pledged assets and net payable receivable for securities purchased sold (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Pledged assets and net payable and receivable for securities purchased sold [Line Items]      
Funds Held Investment Interest Rate Range Low 2.10%pre_FundsHeldInvestmentInterestRateRangeStart 1.80%pre_FundsHeldInvestmentInterestRateRangeStart 2.00%pre_FundsHeldInvestmentInterestRateRangeStart
Funds Held Investment Interest Rate Range High 5.40%pre_FundsHeldInvestmentInterestRateRangeEnd 4.30%pre_FundsHeldInvestmentInterestRateRangeEnd 5.00%pre_FundsHeldInvestmentInterestRateRangeEnd
Restricted Cash and Cash Equivalents $ 172,300,000us-gaap_RestrictedCashAndCashEquivalents $ 200,600,000us-gaap_RestrictedCashAndCashEquivalents  
Marketable Securities, Restricted 2,455,600,000us-gaap_MarketableSecuritiesRestricted 2,477,800,000us-gaap_MarketableSecuritiesRestricted  
Receivable for securities sold 51,586,000pre_ReceivableForSecuritiesSold 150,816,000pre_ReceivableForSecuritiesSold  
Payable for securities purchased (63,779,000)pre_PayableForSecuritiesPurchased (60,153,000)pre_PayableForSecuritiesPurchased  
Net (payable) receivable for securities purchased/sold (12,193,000)pre_NetPayableReceivableForUnsettledTrades 90,663,000pre_NetPayableReceivableForUnsettledTrades  
Equities      
Pledged assets and net payable and receivable for securities purchased sold [Line Items]      
Marketable Securities, Restricted $ 120,000,000us-gaap_MarketableSecuritiesRestricted
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember